In recent years, the ultrathin design of various products is popular in the world, including ultrathin mobile phones, ultrathin TV sets, ultrathin computers and ultrathin light-weight vibration-reduction and noise-reduction devices for military industries and civil application. To meet this requirement, domestic and foreign scholars and engineering technical personnel have carried out a lot of work. However, one of the bottleneck problems is how to achieve the ultrathin design of acoustic impedance converters. For example, for a loudspeaker as an acoustic impedance converter, the quality of tone thereof depends on the size of the end surface aperture of the loudspeaker. For the traditional loudspeaker, the larger the end surface aperture thereof is, the larger the thickness of the loudspeaker is. At present, to achieve the ultrathin design of an acoustic impedance converter, the following several methods are often used, or the structure of acoustic impedance converter is improved so that the components and parts constituting the acoustic impedance converter are compactly arranged in a limited space, for example, patent CN201310042528.0, and the like; or a piezoelectric ceramic sheet is used as an actuating element of a vibration diaphragm, for example, patent CN201010593395.2 and the like; or a flat vibration diaphragm is used, for example, patent CN201310089954.X and the like. Wherein, the development space is extremely limited by improving the structural configuration to achieve the purpose of reducing the thickness of the acoustic impedance converter; however, although the modes of using the piezoelectric ceramic sheet and the flat vibration diaphragm can substantially reduce the thickness of the acoustic impedance converter really, because of the imitation of the material or design principle thereof, the low frequency characteristics thereof are especially inadequate. At present, under the existing technical condition, design personnel can only seek a balance between the performance and required thickness of the acoustic impedance converter.